Sanskrit: Bhujangasana (sounds like boo-jon-goss-a-nuh) भुजङ्गासन
Generally in yoga classes, the first version of cobra is used. Baby cobra (see pic below). You are opening your heart while working on strengthening your back muscles and are holding yourself up using them with little to no pressure on your hands. This is the version of cobra used in Bikram style yoga, or Hot Power Fusion classes, in Vinyasa classes I often see the series of them placed together in order to warm up your back.
In baby cobra, momma cobra or full cobra, you keep your legs tight together like one long tail. Your big toes press into the ground and you keep your thighs also on the ground.